Do you have any colleagues or former bosses who have acted as interviewers on panels before? They will have done the training and be aware of how it works.
I know Carr communications did work in this field, though I wasn't as impressed with them as I subsequently was with a woman who no longer does this work down in County Laois. They were ok and it does help get you in the interview mindset.
The most important thing is to make sure you hit the keywords in the competency structure in your replies, keep them in mind whilst preparing your answers. Is it a fully structured interview with your examples given in advance?